Cursor removes malicious Claude Code extension after SSH backdoor attempt

Publisher excerpt From CSO Online

A malicious version of Anthropic’s Claude Code extension distributed through the Cursor marketplace attempted to install a persistent Secure Shell (SSH) backdoor on developers’ machines, potentially giving attackers remote access to systems holding source code, credentials and other sensitive information. “Between about 2:27am PT and 1:35pm PT today, a maliciously modified version of Anthropic’s Claude Code extension was made available in the Cursor VS Code Extension Marketplace,” Cursor said in a security notice. Cursor removed the compromised versions, 2.1.312 and 2.1.313, after discovering they had been available in its VS Code extension marketplace for approximately 11 hours on October 29. The company said the malicious code attempted to add an attacker-controlled SSH key, enable local SSH access, and establish a reverse tunnel to an attacker-controlled server. “These malicious versions of the extension were not developed by Anthropic,” Cursor added in the notice. The affected versions were available for Windows and macOS. Anthropic subsequently clarified how the tampered extension had been distributed. In a post on X, Felix Rieseberg, a member of Anthropic’s technical staff, said the incident did not involve a compromise of Anthropic’s systems or employee laptops. A malicious actor had used access to Cursor’s marketplace to publish the modified extension, he said. “The versions on our official channels are not affected, and this only impacts Cursor users,” Riesebe…

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